In the NGN, because the carrier network adopts the packet technology, in particular the IP (Internet Protocol) technology, the problems of QoS (Quality of Service) become especially outstanding. The ITU (International Telecommunication Union) has proposed that using the RACF (Resource and Admission Control Function) to solve the QoS problems in NGN carrier networks.
The major function of RACF is to perform resource and admission control based on the user subscription QoS information and available resources in the network, according to operation policies and rules. The RACF blocks the differences of the carrier layer for the application layer and maps the QoS attributes of the application layer to the carrier is layer so that the carrier layer transmission entity can provide QoS assurance for the media flow of the session under its directing. The RACF is comprised of two parts which are the Policy Decision Function Entity (PD-FE) and the Transport Resource Control Function Entity (TRC-FE).
In ITU's latest RACF draft, the functional architecture of the RACF from ITU-T (International Telecommunication Union-Telecom) is shown in FIG. 1.
The PD-FE makes a preliminary QoS resource decision based on the media flow session information acquired from the Service Control Function (SCF) entity through the Rs interface and the user's transmission resource subscription information acquired from the Network Attachment Control Function (NACF) entity through the Ru interface, then interacts with TRC-FE to determine whether there are sufficient QoS resources, and finally makes a final decision and sends the final decision down to the Policy Execute Function Entity (PE-FE) for execution.
The TRC-FE is mainly responsible for resource control. The TRC-FE monitors the resources in the network and collects the related information, and responds according to the specific resource conditions when the PD-FE requests resources.
The PE-FE performs policy control (gate control, bandwidth, traffic classification and tagging, traffic shaping, QoS mapping of Layer 2 and Layer 3, and collecting and reporting resource usage information, etc) primarily under the direction of PD-FE.
The Transport Resource Execute Function Entity (TRE-FE) protocol performs Layer 2 policy execution related to the transmission technology under the direction of TRC-FE according to the current description, but neither the specific functions nor the scope has been determined.
Currently, RACF's resource and admission control mode is classified into two QoS resource control modes, i.e. PUSH and PULL, to adapt to different Customer Premises Equipments (CPEs).
Wherein, the PULL mode refers to the service that SCF requests RACF to perform is QoS resource authorization and resource reservation for the service initiated by CPE and the transmission layer function entity actively requests RACF for a decision when receiving a transmission layer QoS signaling message. The mode is mainly comprised of three processes, i.e. Authorization, Reservation and Commitment, where the latter two processes can generally be combined into a single process.
FIG. 2 illustrates the authorization process in the PULL mode, which specifically includes the following:
(201) A SCF activates the QoS authorization process after receiving the service establishment signaling message.
(202) The SCF requests an authorization for the service by sending a resource initialization request message to a PD-FE.
(203) The PD-FE performs QoS resource authorization for the service request.
Herein, the PD-FE can assign an authorization token to the session, the authorization token may subsequently be carried by the CPE when initiating the resource reservation request and be used for bundling the service flow and the session; the quintuple method can be used to perform identification and bundling if no authorization token is assigned.
(204) The PD-FE replies a resource initialization response to the SCF.
If an authorization token has been assigned, the authorization token would be carried in the response.
(205) The SCF continues service signaling negotiation with a CPE, the SCF would return the authorization token to the CPE through signaling if the PD-FE in the RACF returns an authorization token.
After the authorization process, and after passing the signaling negotiation of QoS through the service layer, the CPE may initiate the resource reservation request process, which involves two situations, one is that the CPE initiates a request through the PE-FE, and the other is that the CPE initiates a request through the local TRC-FE residing in the is transmission layer function entity.
An illustration of the former is as shown in FIG. 3, the CPE first performs service signaling negotiation with the SCF, and after the QoS authorization is performed by the RACF, the CPE may initiate a resource reservation request through the transmission layer signaling, and activate the PE-FE of the transmission layer function entity to initiate a resource reservation request to the PD-FE.
An illustration of the latter is as shown in FIG. 4, the CPE first performs service signaling negotiation with the SCF, and after the QoS authorization is performed by the RACF, the CPE may initiate a resource reservation request through the transmission layer signaling, and activate the local TRC-FE residing in the transmission layer function entity to initiate a resource reservation request to its upper layer TRC-FE, i.e. the TRC-FE of the carrier control layer; after checking the available resources to ensure that they can meet the request, the upper layer TRC-FE may then request a resource and admission decision from the PD-FE.
Among existing methods for resource and admission control of the PULL mode, because multiple PD-FEs may exist based on different service scenarios, there are multiple-to-one and one-to-multiple scenarios between PE-FEs, the carrier control layer TRC-FE and PD-FE, as shown in the networking illustration in FIG. 5. In this case, the PE-FE or carrier control layer TRC-FE can not figure out which PD-FE has authorized the service flow that initiated the resource reservation request, thereby can not select the exact PD-FE to implement the resource reservation request process, after receiving the resource reservation request.
Therefore, it is necessary to improve the existing PULL mode based method for resource and admission control so as to solve this problem.